Articles | Volume 7, issue 2
Review article
16 Nov 2015
Review article |  | 16 Nov 2015

CO2-flux measurements above the Baltic Sea at two heights: flux gradients in the surface layer?

A. Lammert and F. Ament

Abstract. The estimation of CO2 exchange between the ocean and the atmosphere is essential to understand the global carbon cycle. The eddy-covariance technique offers a very direct approach to observe these fluxes. The turbulent CO2 flux is measured, as well as the sensible and latent heat flux and the momentum flux, a few meters above the ocean in the atmosphere. Assuming a constant-flux layer in the near-surface part of the atmospheric boundary layer, this flux equals the exchange flux between ocean and atmosphere. The purpose of this paper is the comparison of long-term flux measurements at two different heights above the Baltic Sea to investigate this assumption. The results are based on a 1.5-year record of quality-controlled eddy-covariance measurements. Concerning the flux of momentum and of sensible and latent heat, the constant-flux layer theory can be confirmed because flux differences between the two heights are insignificantly small more than 95 % of the time. In contrast, significant differences, which are larger than the measurement error, occur in the CO2 flux about 35 % of the time. Data used for this paper are published at

Short summary
The paper presents long-term measurements of turbulent fluxes at the research platform FINO2 in the Baltic Sea. The platform was equipped at two heights (6.8 and 13.8m) for the observation of wind, temperature, humidity and CO2 over a time period of 1.5 years. The paper shows the measured quantities as well as the turbulent fluxes, latent and sensible heat, momentum and CO2 flux. In contrast to the constant-flux layer approach, we found differences in the CO2 fluxes between 6.8 and 13.8m.